Top 3 Things That Can Drain Car Batteries in Winter

  • Nov 19,2018
guy wearing a brown coat checking a car battery in winter guy wearing a brown coat checking a car battery in winter

Freeze! You aren’t going anywhere. Not with a dead car battery, at least. Christmas dinner at Grandma’s house will have to wait.

Keep your holiday travels on track by watching out for things that can weaken and drain your car battery, especially in cold weather.

How Your Car Battery Works

Before we jump into what drains a car battery, let’s take a quick detour to understand the basics of how a battery works.

The battery in your car contains energy cells and a special lead-acid chemical solution that work together to provide a jolt of energy to get things moving and grooving when you turn your key in the ignition.

As NASA puts it, a battery “translates chemical energy into electrical energy.”

Without the battery, your car's engine won't start and the electronics won't work.

Top 3 Things That Drain Your Car Battery in Winter

Drain #1: Human Error

Unfortunately, the number one drain on your car battery is most often, well, you! In winter, it can be tempting to rush inside and cozy up in front of the fireplace. But before you do, check that you’ve totally powered down your vehicle and all of its accessories to avoid a dead battery.

  • Make sure your interior lights and headlights are off. Some cars’ headlights turn off automatically after a certain amount of time but double-check yours anyway. Also, check to make sure your car doors are completely shut. If a door is left ajar, your interior lights can stay on and drain the car battery.
  • Unplug all accessories. We recommend unplugging everything that draws power, including your cell phone charger, for a few reasons. In some vehicles, the USB ports and cigarette lighter socket receive power even when the car is turned off. Also, when you turn the key, your car battery provides a zap of electricity to start the engine. When other electronics are plugged in when you start the car, they can steal some of that energy. Don’t shortchange your car battery in cold weather! Give it all the power it needs to get you going.
  • Turn electronics off when the engine's off. Your battery is designed to power some electronics while the engine is off, but only for a limited time. Avoid running your radio, GPS, or other electronics for more than 20 minutes when the engine is off to help the battery maintain its charge.

Drain #2: Corrosion or Loose Cable Connections

There are two points of contact on top of your battery—one positive, one negative. These are called terminals, and they stick out like posts on top of the battery. Your car has cables that connect to these posts.Gloved hand removing car battery terminal to clean the battery

Corrosion around the terminals or loose cable connections can interfere with the battery charge and make it harder for the battery to start your engine. A quick terminal cleaning and cable check can help reestablish contact.

  • Clean your battery terminals. Inspect your battery. If you notice a white, powdery substance around the terminals that looks like dead skin on dry hands, you’ve got a case of corrosion. Use a dry rag to wipe off dirt, grime, and corrosion from around the battery terminals. You can even scrub them with some baking soda, water, and a toothbrush. Reader’s Digest also recommends adding petroleum jelly to prevent future corrosion.
  • Tighten loose battery cable connections. The cables that connect your battery to your car can naturally loosen over time. Consult your owner's manual and if you're comfortable doing so, use a wrench to tighten the connections. If not, stop by your nearest Firestone Complete Auto Care for help.

Drain #3: Freezing Temperatures

Cold weather slows everything down, especially the chemical reaction happening inside your car battery. In fact, at 32°F, a car’s battery loses about 35% of its strength. And at 0°F, it loses up to 60% of its strength—but your engine requires nearly twice as much power to start!

Have you ever tried sucking molasses through a straw? That’s kind of how your car battery feels in winter weather. Luckily, you can help keep your car battery charged in the cold by taking the following precautions:

  • Install a battery blanket. You can purchase one for around $20 online or at a local auto parts store. Simply plug the blanket in, wrap it around your battery, and enjoy a smooth start tomorrow morning. Just make sure you follow the instructions that come with the battery blanket!
  • Park your car in the garage or away from the wind. Leave your car in a garage overnight to help protect the battery. If you don’t have a garage, park the front of the car downwind.
  • Give it a charge. A fully charged battery won’t freeze until -76°F, while a fully discharged battery could start freezing around 32°F. Is your battery fully charged for winter? Let one of our techs check!

If you have car battery drain on the brain, it's time for a free battery check. Trust us. It’s worth it. Our technicians know batteries and install more than 800,000 car batteries a year using. Visit your local Firestone Complete Auto Care for a free battery check today.

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